Method of insulating conductors



R. R. WILLIAMS Y 4 METHODDF INSULATING CONDUCTORS 0dw 3o, 192s. 1,689,312

Filed April 2, 1924 nlyn .lalala oa.- 1928- UNITED STA-TES Pan'ala"l OFFICE# .I

nomina* n mums, or nosELLE, Naw JERSEY, As'sIGNoa' 'ro waaraan Ennesimo' Y conm, moonromrnn, or-Nnw Yonx, n, Y., A conromrIoN orA NEW Yom METHOD F INSULATING CONDUCTOBS.

Application ined April 2,

This invention relates to electrical conduc-l 'tors and more particularlyv to the insulated electrical conductors of submarine cables.

. It is an object of the invention to improve y5 the insulation of such conductors both electrically and mechanically and to applythe insulating material to the conductor in such a manner as not to deleteriously affect the conductor itself. and in the case of a loadedcon- 10. ductor, to apply the insulating material so 25 furthermore, the extent vof the sulphur attack on the conductor is objectionable during the long period of heating. Moreover vulcanization of the rubber compound on `the conducisfactory result in the case of a continuously e loaded conductor of the type recently developed. In this conductor, a' recently discovered4 alloy is employed for the loading material, such an alloy having a permeability at low magnetizingiorces far'in excessof that `obtained with thebest iron wireheretoforb employed forcontinuous loading. However,

' to obtain the best results with this new alloy when usedin a submarine cable, kit is neces# 40 sary to protect-it from mechanical strains induced by hydrostatic pressure vexerted on it atsea bottom .and to protect against such' strains it has beenxfound desirable to impregnate the loaded conductor with an insulating compound such l.as liquid bitumen that fills al1 the' interstices between adjacent turnsv of the loading 'materialand between the loading material and the conductor itself and also in the case of a stranded conductorbetween adiacent strands of the conductor. .To this end, it is preferable to employ an -impregnating material which is fluid .atthe temperature encountered in A great depths of water. a Co`mplete disclosures of the new loading material and its application to submarine cable foontor cannot be accomplished so as to give a sat- 1924. Serial No. 703,660.

lductors are found in'patents to G. W. Elm'en' No. 1,586,884 and 0. E.' Buckley Nos.

1926. It is not satisfactory. to vulcanize'the rubber compoundv on a core of this type in v which a layer of liquid bitumen isprovided 1,586,874and 1,586,87 5, allv issued on June 1,

under the insulating material since the liquid n bltumen mixes with the rubber compound during vulcanization and hardens to such anextent as to render it useless in protecting the loading material from subsequent strains.

To provide an insulated 'conductor having the desired characteristics, the invention contemplates the use of an insulating compound which is rst vulcanized then rendered plastic and extruded in a continuous sheath about the conductor by means of heat and pressure. In the accompanying drawing, Fig. 1 is a sectional view of an extruding press by means of whichthe plastic mass of prevulcanized rubber is extruded about the conductor, and

ductor made in accordance with the features .of this invention. y

In practicing this invention,sheets of vul canized hard rubber are rendered plastic by working them in 'standard rubber mills,vv the rolls. of which are heated, or in -some other yso Fig. 2 is a view of a continuously loaded conl equivalent manner. The term hard rubberz I.

is here used to also include these compositions sometimes referred to as semi-hard rubber in" which the sulphur .component may be' as low as 15 per cent. In order that thevulcan- 1 ized sheets may be more easily rendered sui'- f ciently plastic topermit the material being 95 A.

extruded, it is desirable to include inthe rubber compound a thermoplastic material such vas a bitumen. preferably of one of the harder varieties. -While the composition of the insuto 2000 pounds per square-inch consists of approximately- 60% rubber, V20% sulphur and 20% bitumen vulcanized at temperatures corresponding to tol 100 pounds steam pressure until the free sulphur content is reduced.

to .5`per cent or less in a manner such as is now commonly employed in the hard rubber, industry. In place of .or in addition to adding'a bitlnnen torender the vulcanized com f poundfmore thermoplastic, -it is possible to use, in whole or in part, thematerial made in f' vas which the extruding material passes as itV leaves the hopper, being forced along by means of a rotating Worm 6 driven by gear 7 The gear and Worm are provided with a hollow central portiony through which the conductor to be insulated is 'driven at a predetermined rate by means not shown. As4

the conductor emerges through the end of the Worm 6, it passes through the compressed plastic mass andthe die 9 held in position y. a retaining plate 10 maintains the desired outer diameter of the insulated con ductor. In order to maintain the insulating material in a plastic condition until after it is extruded, the press is provided with jackets 11, 11 through which live steam is passed from pipes 12, 12. A steam pressure is preferably maintained so as to insure a suiable temperature of approximately 150 In Fig. 2 there is shown the inished con- Ilductor comprising a central core 15 sur- A rounded by conductor lstrands 16, -16 about which is helically Wrapped the loadingmaterial 17 over which is placed a coating o liquid bitumen 18. The conductor completed thus far is passed through' the extruding press Where itis provided with a Sheath 19 of prevulcanized insulating compound.

What is claimed is:

1. The method of insulating a conductor which consists in forming thereabout a con-v tiguous and continuous single layer of prevulcanized hard rubber. Y

2. The method of. insulating a Aconductor which consists in extruding thereabout prevulcanized hard rubber .by the application.'

of heat and pressgre. n d. -3. The method of insulating aconductor whichv consists in vulcanizing the insulatmg material, rendering the vulcanized material plastic and extruding said material about the conductor by the application of heat and pressure.

4. The method of insulating 'a conductor with vulcanized hard`rubbewlich method consists in rendering the vulcanized rubber plastic and immediately extruding said vul-' canized rubber about the conductor by suitable application of heat and pressure.

5. The method of insulating a conductor `With a vulcanizable material containing approximately 20% bitumens which method consists in vulcanizing the insulating material, rendering it plastic by milling v'with heated rolls, and immediately extruding said material about the conductor.

6. The method of insulating a conductor which consists in vulcanizing sheets of a rubber compound including hardV bitumen vulcanized at a temperature corresponding to `approximately 95 pounds steam pressure,

rendering said compound Vplastic by milling Y With heated rolls, and extrudmg said compound about the conductor by means ofthe application of suitable heat and pressure.

7. The method of producing a conductor i continuously loaded with magneticmaterial of high permeability and sensitive to mechanical strain which comprises applyingv the loading material to the conductor, 1mpregnating the loaded conductor with a substance poorly adapted to remain in situ-unchanged by the4 heat necessary forY vulcani-I zation, and forming thereabout a'contiguous and continuous single layer of prevulcanized hard rubber. .Y

8. The method of producing a layer of vulcanized insulating material upon a. conductor loaded with strain sensitive magnetic material Without detrimentally aiecting the properties of a compound in which the loading material is imbeddedv to relieve it from strain which comprises first vulcanizing the insulating material, rendering it plastic, and

then extruding it about the compound by Vthe application of heat and pressure.

In Witness whereof, I hereunto lsubscribe my name this 27th day o'MarchA. D., 1924.-.

ROBERT R. 

